Shear force improves high pressure dewatering

An interdisciplinary research project at the University of Melbourne has “re-imagined” technology used for crushing rocks, creating a novel way to remove water from materials as varied as recycled paper, mineral slurries and microalgae.

The work is part of a collaborative industry project with packaging manufacturer Visy Industries to improve the efficiency of dewatering in its paper and cardboard recycling processes.

Filters, centrifuges and thickeners all use compression to squeeze water out of suspensions. The new prototype for Visy compresses suspensions between two high-pressure dewatering rollers. Water can pass through the surface of the rollers, but the suspended solids cannot. A vacuum in each roller helps to pull the suspension onto the rollers and extract water.

Most importantly, the rollers also turn at different speeds. This adds a shearing force, which makes water extraction more effective.

Identifying the characteristics of different suspension, such as how the water flows through the suspended solids, allows the speed of the rollers to be adjusted to ensure the shear force applied maximises dewatering.

Dr Stickland says the prototype has the potential to improve water extraction from suspensions compared with current industrial practices. In processes where further drying is needed before solids are used, or disposed of, it also has the potential to reduce costs, because less water needs to be evaporated.

In a related project, Dr Stickland’s research team has also been working with algae producer MBD Energy on a prototype to dewater microalgae. This project was funded through a Victorian Government Technology Voucher, as more efficient dewatering has the potential to improve the commercial viability of industrial algal production.